Pentax MX and Prinzflex Auto 3X Converter

Hello,
I've bought a Pentax MX that came with 3 lenses...and this Prinzflex converter. I really cannot understand how to use with my lenses because i have a the PK/M42 (i suppose) adapter ring to connect to the camera side(PK/M42 female) , but i should have another M42/PK (M42 male/PK) mount to connect it to my lenses...i said 'i should' because i can't understand if i'm misunderstanding something!

This converter will only work if you find some screw mount (M42) lenses.
A screw mount 3x converter is likely not very high quality, Likely not worth the investment in more glass?
It should be faster glass too, you'll lose 3-stops of light with it,

This converter will only work if you find some screw mount (M42) lenses.
A screw mount 3x converter is likely not very high quality, Likely not worth the investment in more glass?
It should be faster glass too, you'll lose 3-stops of light with it,